optic neuritis

Optic Neuritis

Definition

Optic neuritis is a vision disorder characterized by inflammation of the optic nerve.

Description

Optic neuritis occurs when the optic nerve, the pathway that transmits visual information to the brain, becomes inflamed and the myelin sheath that surrounds the nerve is destroyed (a process known as demyelination). It typically occurs in one eye at a time (70%), and the resulting vision loss is rapid and progressive, but only temporary. Thirty percent of patients experience occurrence in both eyes. Optic neuritis tends to afflict young adults with an average age in their 30s. Seventy-five percent of patients with optic neuritis are women.

Nerve damage that occurs in the section of the optic nerve located behind the eyeball, is called retrobulbar neuritis, and is most often associated with multiple sclerosis. Optic nerve inflammation and edema (swelling) caused by intracranial pressure at the place where the nerve enters the eyeball is termed papillitis.

Causes and symptoms

Symptoms of optic neuritis include one or more of the following:

blurred or dimmed vision

blind spots, particularly with central vision

pain with eye movement

headache

sudden color blindness

impaired night vision

impaired contrast sensitivity

Optic neuritis is most commonly associated with multiple sclerosis (MS). Other causes include viral or fungal infections, encephalomyelitis, autoimmune diseases, or pressure on the nerve from tumors or vascular diseases (i.e., temporal arteritis). Some toxins, such as methanol and lead, can also damage the optic nerve, as can long-term abuse of alcohol and tobacco. Patients with non-MS related optic neuritis are usually immunocompromised in some way.

Diagnosis

An ophthalmologist, a physician trained in diseases of the eye, will typically make a diagnosis of optic neuritis. A complete visual exam, including a visual acuity test, color vision test, and examination of the retina and optic disc with an ophthalmoscope, will be performed. Clinical signs such as impaired pupil response may be apparent during an eye exam, but in some cases the eye may appear normal. A medical history will also be performed to determine if exposure to toxins such as lead may have caused the optic neuritis.

Further diagnostic testing such as magnetic resonance imaging (MRI) may be necessary to confirm a diagnosis of optic neuritis. An MRI can also reveal signs of multiple sclerosis.

Treatment

Treatment of optic neuritis depends on the underlying cause of the condition. Vision loss resulting from a viral condition usually resolves itself once the virus is treated, and optic neuritis resulting from toxin damage may improve once the source of the toxin is removed.

A course of intravenous corticosteroids (steroids) followed by oral steroids has been found to be helpful in restoring vision quickly to patients with MS-related episodes of optic neuritis, but its efficacy in preventing relapse is debatable. The Optic Neuritis Treatment Trial (ONTT) has shown that IV steroids may be effective in reducing the onset of MS for up to two years, but further studies are necessary. Oral prednisone has been found to increase the likelihood of recurrent episodes of optic neuritis, and is not recommended for treating the disorder.

Prognosis

The vision loss associated with optic neuritis is usually temporary. Spontaneous remission occurs in two to eight weeks. Sixty-five to eighty percent of patients can expect 20/30 or better vision after recovery. Long-term prognosis depends on the underlying cause of the condition. If a viral infection has triggered the episode, it frequently resolves itself with no after effects. If optic neuritis is associated with multiple sclerosis, future episodes are not uncommon. Thirty-three percent of optic neuritis cases recur within five years. Each recurrence results in less recovery and worsening vision. There is a strong association between optic neuritis and MS. In those without multiple sclerosis, half who experience an episode of vision loss related to optic neuritis will develop the disease within 15 years.

Organizations

Key terms

Multiple sclerosis — An autoimmune disease of the central nervous system characterized by damage to the myelin sheath that covers nerves.

Temporal arteritis — Also known as giant cell arteritis. Inflammation of the large arteries located in the temples which is marked by the presence of giant cells and symptoms of headache and facial pain.

Visual acuity test — An eye examination that determines sharpness of vision, typically performed by identifying objects and/or letters on an eye chart.

neuritis

[noo͡-ri´tis]

inflammation of a nerve; also used to denote certain noninflammatory lesions of the peripheral nervous system. There are many forms with different effects; some increase or decrease sensitivity of the body part served by the nerve, others produce paralysis, and some cause pain and inflammation. The cases in which pain is the chief symptom are generally called neuralgia. See also neuropathy. adj., adj neurit´ic.

Neuritis and neuralgia attack the peripheral nerves, the nerves that link the brain and spinal cord with the muscles, skin, organs, and all other parts of the body. These nerves usually carry both sensory and motor fibers; hence both pain and some paralysis may result. Treatment varies with the specific form of neuritis involved.

Generalized Neuritis. Certain toxic substances such as lead, arsenic, and mercury may produce a generalized poisoning of the peripheral nerves, with tenderness, pain, and paralysis of the limbs. Other causes of generalized neuritis include alcoholism, vitamin-deficiency diseases such as beriberi, and diabetes mellitus, thallium poisoning, some types of allergy, and some viral and bacterial infections, such as diphtheria, syphilis, and mumps. Some attacks begin with fever and other symptoms of an acute illness. However, neuritis caused by lead or alcohol poisoning comes on very slowly over the course of weeks or months. Usually an attack of generalized neuritis will subside by itself when the toxic substance is eliminated. Rest and a nutritious diet containing extra vitamins, especially of the B group, are helpful. Physical therapy may relieve the pain and paralysis. Generalized neuritis may be prevented through knowledge of the dangers of poor nutrition, industrial hazards, chronic alcoholism, and infections.

Special Types of Neuritis. Frequently, instead of a generalized irritation of the nerves, only one nerve is affected. bell's palsy, or facial paralysis, results when the facial nerve is affected. It usually lasts only a few days or weeks. Sometimes, however, the cause is a tumor pressing on the nerve, or injury to the nerve by a blow, cut, or bullet. In that event, recovery depends on the success in treating the tumor or injury.

Sciatica is inflammation of or injury to the sciatic nerve, a large nerve running downward from the spinal cord into the lower limb. The most common cause is probably a herniated disk. Back injury, irritation from arthritis of the spine, or pressure on the nerve from certain types of work are other causes. Certain diseases such as diabetes mellitus or gout may also be inciting factors. (See also sciatica.)

Neuritis of the Spinal Nerves. Injury or disease may affect any of the many nerves traveling out from the spine. For example, inflammation of the nerves between the ribs causes pain in the chest that may resemble pleurisy or even coronary occlusion (heart attack). This is called intercostal neuritis or intercostal neuralgia. Similarly, the nerves traveling down the neck to the arm may be subject to various injuries or diseases. For example, too vigorous pulling on the nerves in the neck of a fetus, as in difficult obstetrical deliveries, causes the condition known as brachial paralysis.

Neuritis of the Cranial Nerves. Bell's palsy results from inflammation of the seventh cranial, or facial nerve. The fifth cranial, or trigeminal, nerve, also ends in the face and jaws, and may be the source of a neuralgia that causes spasms of pain on one side of the face, called tic douloureux or trigeminal neuralgia. It may be set off by a draft of cold air, by chewing, or by other factors. Medicines and, if necessary, surgery can relieve this painful malady.

Optic neuritis refers to any of various conditions in the nerves leading to the retina of the eye; this is potentially dangerous to vision and requires immediate treatment. Any of the other cranial nerves may be affected by infections, tumors, and toxins. The antibiotic streptomycin occasionally causes damage to the eighth cranial nerve, which helps control the sense of balance in the inner ear. Any disturbance of vision, hearing, balance, swallowing, taste, or speech may be a sign of trouble in the cranial nerves, and should be immediately brought to the attention of a health care provider.

op·tic neu·ri·tis

optic neuritis

Inflammation of the optic nerve. This is sometimes due to infection but is most commonly due to DEMYELINATION as in MULTIPLE SCLEROSIS. There is tenderness on pressure on the eye and on extremes of movement but the most striking effect is loss of vision over the central part of the field of vision of the eye on the affected side. Recovery, in about 6 weeks, is usual but there may be some permanent loss of visual acuity or colour sensitivity. There is no effective treatment.

neuritis, optic

Inflammation of the optic nerve, which can occur anywhere along its course from the ganglion cells in the retina to the synapse of these cell fibres in the lateral geniculate body. If the inflammation is restricted to the optic nerve head the condition is called papillitis (or intraocular optic neuritis) and if it is located in the orbital portion of the nerve it is called retrobulbar optic neuritis (or orbital optic neuritis).In papillitis the optic nerve head is hyperaemic with blurred margins and slightly oedematous. Haemorrhages and exudates may also appear. In retrobulbar optic neuritis, there are usually no visible signs in the fundus of the eye until the disease has advanced and optic atrophy may appear. However, both types are accompanied by a loss of visual acuity along with a central scotoma and impairment of colour vision. The loss of vision may occur abruptly over a few hours and recovery may be equally rapid but in some patients the loss may be slow. In retrobulbar optic neuritis, there is also pain on movement of the eyes and sometimes tenderness on palpation. The disease is usually unilateral although the second eye may become involved later. It is usually transient and full or partial recovery takes place within weeks. The primary cause of optic neuritis is multiple sclerosis but it may also be associated with severe inflammation of the retina or choroid, vitamin B deficiency, diabetes mellitus, thyroid disease, lactation, toxicity or syphilis. SeeDevic's disease; papilloedema; Marcus Gunn pupil; Kollner's rule; photostress test.

op·tic neu·ri·tis

(op'tik nūr-ī'tis)

Inflammation of the optic nerve.

neuritis

pl. neuritides; inflammation of a nerve; also used to denote noninflammatory lesions of the peripheral nervous system. See also neuropathy.

There are many different forms of neuritis. Some increase or decrease the sensitivity of the body part served by the nerve; others produce paralysis; others cause pain and inflammation. The cases in which pain is the chief symptom are generally called neuralgia.

Neuritis and neuralgia affect the peripheral nerves, the nerves that link the brain and spinal cord with the muscles, skin, organs, and all other parts of the body. These nerves usually carry both sensory and motor fibers; hence both pain and some paralysis may result.

Raju Kapoor (National Hospital, London) is testing whether the epilepsy drug phenytoin can reduce or prevent nerve fiber injury in 90 people with optic neuritis, an eye disorder that's often the first sign of MS.

The patients who were provisionally diagnosed with demyelinating disease, MS, optic neuritis or paraplegia during the field visits by the field teams were invited to the hospital to be examined by a neurologist blinded to the study.

Cullen presents a case report on an unusual case of optic neuritis in an HIV-infected patient, and in a review article Garone and colleagues discuss the progress to date and lessons learned from 10 years of programmes delivered through Medecins Sans Frontieres in Khayelitsha, Cape Town.

Such strategies include glucocorticoids and immunosuppressant therapy "when the underlying pathogenesis is considered primarily inflammatory (such as in optic neuritis, transverse myelitis, or psychosis) or there is evidence of generalized SLE activity"; and antiplatelet/antithrombotic therapy for moderate to high antiphospholipid antibodies or other features of antiphospholipid antibody syndrome, particularly thrombotic cerebrovascular disease, according to the guidelines.

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